1. Field of the Invention
The present invention relates to a method and system for determining abnormities in a dataset, and more particularly to a method and system for determining a defect during sample inspection involving charged particle beam imaging.
2. Description of the Prior Art
Charged particle microscopic images are formed by detecting charged particles released from a sample being bombarded by a charged particle beam. Analyzing the charged particle microscopic images can obtain desired information of the physical and electrical characteristics of the inspected sample. For example, the charged particle beam imaging technique is applied to inspection of semiconductor device, and by analyzing the obtained image of the semiconductor device the presence of defects in the concerned device can be determined.
FIG. 1 illustrates the conventional defect determination method for inspection of a wafer 1 and a plurality of chips arranged on the surface of wafer 1. A method for determining a defect according to a prior art includes comparing an image of corresponding regions 111, 121, 131 within the repeating chips 11, 12, 13, by for example an arithmetic program. If the comparison result gives a signal value which exceeds a predefined threshold, it is determined that there is at least one defect within one of the chips 11, 12, 13. The comparison method of the prior art is based only on a feature gray value for each image of respective regions 111, 121, 131. For example, gray values at different locations within a single image are averaged to produce a global feature gray value for that image. Then, the feature gray values of each image are compared to determine if there is a defect existing within one of the regions 111, 121, and 131. Because the method of the prior art is oversimplified, misjudgment frequently occurs in the inspection. For more precise comparison, more factors should be considered for an image being observed.
According to the foregoing descriptions, a method and system able to more precisely determine the presence of a defect within the charged particle microscopic image and reduce the occurrence of misjudgment is highly desired in the field.